The present invention relates to an organic luminescence device using a specific fused polynuclear (or polycyclic) compound, particularly an organic luminescence device wherein an electric field is applied to a film of an organic compound comprising the fused polynuclear compound thereby causing luminescence.
An organic luminescence device is a device such that a thin film containing a fluorescent organic compound is sandwiched between an anode and a cathode, and holes and electrons are injected from the anode and the cathode, respectively, into the fluorescent organic compound layer to generate excitons which emit light when returned to a ground state.
For example, according to Eastman Kodak""s study, Appl. Phys. Lett., vol. 51, p. 913 (1987), when a voltage of about 10 volts is applied to a function separation-type organic luminescence device including two layers of an aluminum quinolinol complex (as electron transport and luminescence material) and a triphenylamine derivative (as hole transport material) disposed between an ITO (indium tin oxide) anode and a magnesium-silver alloy cathode, an emission luminance of about 1000 cd/m2 is obtained. Related patents thereto are, e.g., U.S. Pat. Nos. 4,539,507, 4,720,432, and 4,885,211.
Further, it is possible to effect luminescence ranging from the ultraviolet region to the infrared region by appropriately changing the species of fluorescent organic compound used. In recent years, studies on various fluorescent organic compounds have been made extensively as, e.g., described in U.S. Pat. Nos. 5,151,629, 5,409,783, and 5,382,477; and Japanese Laid-Open Patent Application (JP-A) Nos. 2-247278 (corr. to U.S. Pat. Nos. 5,130,603 and 6,093,864), 3-255190 (corr. to U.S. Pat. No. 5,227,252), 5-202356, 9-202878, and 9-227576.
In addition to the above-mentioned organic luminescence devices using low molecular weight materials, an organic luminescence device using a conjugated system polymer has been reported by a research group at Cambridge University (Nature, vol. 347, p. 539 (1990)). According to this report, by forming a single layer of PPV (polyphenylenevinylene) by means of wet coating, luminescence from the layer has been confirmed.
Related patents as to organic luminescence devices using conjugated system polymers may include: U.S. Pat. Nos. 5,247,190, 5,514,878, and 5,672,678 and JP-A 4-145192 (corr. to U.S. Pat. Nos. 5,317,169 and 5,726,457) and JP-A 5-247460.
As described above, recent progress with respect to organic luminescence devices is noticeable. More specifically, it is possible to realize a thin and lightweight luminescence device allowing high luminance at low applied voltage, variety of emission wavelengths and high speed responsiveness, thus suggesting possibilities of application to various uses.
However, the organic luminescence devices are required to exhibit further improved performances such as light output at high luminance and high conversion efficiency. Further, the organic luminescence devices have been accompanied with problems in terms of durability such as a change in luminance with time due to continuous use for a long time and deterioration (e.g., an occurrence of dark spots due to leakage of current) by ambient gas containing oxygen or by humidity.
As fluorescent organic compounds for use in an electron injection layer and/or an electron transport layer, a large number of heterocyclic compounds have been proposed as described in, e.g., JP-A 6-184125, 9-286980 and 9-291274. However, resultant emission luminances and durabilities and luminescence efficiencies have still been insufficient.
A principal object of the present invention is to provide an organic luminescence device having solved the above-mentioned problems.
A specific object of the present invention is to provide an organic luminescence device capable of effecting output of light with very high efficiency and luminance using a specific fused polynuclear aromatic compound.
Another object of the present invention is to provide an organic luminescence device having high durability.
A further object of the present invention is to provide an organic luminescence device which can be prepared readily and relatively inexpensively.
According to the present invention, there is provided an organic luminescence device comprising a pair of an anode and a cathode and at least one organic layer disposed between the anode and the cathode, wherein the at least one organic layer described above comprises a layer comprising at least one species of a fused polynuclear compound represented by the following formula (I): 
wherein R1 to R12 independently denote a hydrogen atom, an alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a substituted amino group, a cyano group or a halogen atom; R1 to R4, R5 to R8 and R9 to R12 being independently capable of including adjacent two groups forming a substituted or unsubstituted aliphatic cyclic structure, a substituted or un-substituted aromatic ring structure, or a substituted or unsubstituted heterocyclic structure, and X1, X2 and X3 independently denote an oxygen atom, a sulfur atom, C(CN)2, C(CF3)2, C(Ar1)Ar2 or Nxe2x80x94Ar3, wherein Ar1, Ar2 and Ar3 independently denote a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group, Ar1 and Ar2 being capable of forming a ring structure.
In the above formula (I), at least one of X1, X2 and X3 may preferably be C(CN)2. Particularly, X1, X2 and X3 may desirably be C(CN)2 at the same time as shown by the following formula (II): 
In another preferred embodiment, X1, X2 and X3 may desirably be O (oxygen atom) at the same time as shown by the following formula (III): 
Further, in the present invention, the above-mentioned layer of fused polynuclear compound of formula (I), preferably formula (II) or (III), may desirably be any one of an electron injection layer, an electron transport layer and a hole blocking layer.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.